CPR instruction involves teaching both the theory of artificial resuscitation and external heart massage and practical techniques for application of the theory. Students can practise artificial breathing techniques on one another, but, often there is a reluctance to do this in a classroom environment because of the intimate nature of the mouth to mouth ventilation method and because of concerns about the transmission of disease. On the other hand, the techniques of external cardiac massage are too aggressive to be practised fully on other students. Consequently, there has been a demand for the manufacture of manikins which will enable students to practise both the ventilation and external heart massage techniques of CPR.
There are many complex and interrelated functions and structures of the human body that are pertinent to the application of both ventilation and cardiac massage resuscitation techniques. Some of the features that are sought to be obtained in a CPR manikin are; a hygienic system which will prevent the transmission of disease from one student to another, a moveable head to permit positioning for throat clearance, a realistic anatomy showing body features which serve as indicators or "landmarks" to locate points of administration, a moveable chest which visually demonstrates breathing during ventilation, a means for measuring and changing volume of air to simulate adults and children, a compressible chest cavity which provides realistic resistance.
Many different systems have been developed for manikins to reduce transmission of germs and viruses. Some manikins are adapted to be cleaned with cleaning solutions after each student uses the manikin. In other manikins, a removable face piece or mask is provided to fit onto the head to be exchanged for a clean one as each student takes a turn. Some manikins have disposable lower airways or lungs to be replaced in the manikin after each student.
The other structural and functional features desired in a manikin are obtained in varying degrees by different manufacturers. Some take pains to replicate the human features even to the extent of attempting to duplicate the texture and feel of human skin. Various types of internal plumbing are used to simulate the airways of the body and sometimes electronics are incorporated into the manikin to produce electrical signals or computer displays relevant to the administration of the techniques. Some manufacturers have patented some manikins or devices for practising ventilation techniques. The applicant is aware of U.S. Pat. Nos. 2,904,898 and 3,068,590, French patent 1,207,372 and Australian Patent 270,640. However, these devices do not provide a means for practising the full CPR techniques. Others have developed manikins to provide both ventilation and external massage, but, it seems to the applicants that the trend in the manufacture of CPR manikins has been towards technical sophistication which in turn has led to the development of expensive manikins. The basic CPR manikins that are known to the applicants cost hundreds of dollars, others cost more than a thousand dollars.
No doubt the sophistication of the CPR manikin technology is useful to instruction of some students, perhaps in cases where advanced courses are being taken. It is the perception of the applicants, however, that there is a public interest in providing basic CPR training to many people since it is usually applied in an emergency situation where it may not be practical to wait until a CPR expert arrives at the scene. It is believed that simple techniques can be effective and that the more people that know the techniques the more likely that there will be someone available to assist an emergency victim. Regular and frequent practise is seen by the applicants to be an important feature of any CPR instruction program and to retention of the skills learned. Applicants believe therefore that it may be disadvantageous to have only expensive manikins available for teaching programs aimed at providing basic skills to many people. It will be appreciated that most instructors would not be able to afford more than 1 or 2 of these expensive manikins for each class. Therefore students must take turns on the manikin. There is less opportunity to practise and teaching is time inefficient where students are waiting to practise. While there may be some benefit in watching others practise it is the applicants' view that it would be more beneficial to instruction and more efficient to have all students practise together as a class on separate manikins. Moreover, if manikins were inexpensive students might obtain a manikin for practise at home to retain their skills after completion of the course.
It is also believed that there is a need for a readily portable manikin to enable an instructor to travel from one location to another to provide instruction. Many prior art manikins are believed to be too large and cumbersome for a single instructor to transport conveniently in large numbers. Applicants believe that an instructor should be able to carry many manikins in a hand held or over the shoulder carrying case.
In U.S. Pat. No. 4,984,987 the applicants disclosed an inexpensive, readily portable manikin to serve as a teaching tool for a basic CPR instruction course. The manikin comprised in combination a head means, a chest means, a disposable lung means, and a compression means in which;
the head means has an opening to receive air blown into it by a user, PA1 the chest means is adapted to be removably connected to the head means, PA1 the disposable lung means is adapted to be removably connected to the head means within the chest means, in communication with the opening of the head means, the compression means is adapted to fit within the chest means to receive compression administered by a user.
The head means of this manikin was said to be a hollow head which will avail itself to mass production techniques. The head has a mouth and nostril openings for artificial resuscitation. The head has a neck portion which is adapted to be connected to a disposable lung bag to receive the air blown into the head. The neck was also adapted to connect into a opening in the chest means. The chest means was a simple shell to provide a visual impression of a torso with anatomical indicators or reference points to assist one to locate the correct position for hand placement during application of the compression heart massage techniques. The front and back portions of the chest were said to be separated by a resilient compression means.
The compression means was described as being adapted to be fitted within the chest means at a predetermined location where external massage would be given. It is compressed by a user attempting to practise external heart massage and resiliently restores itself as the compression is removed. U.S. Pat. No. 4,984,987 taught that the compression means could be manufactured in many ways with different materials including a compressible foam, a hydraulic or pneumatic piston, a spring and an "accordion" folded flexible member. The preferred form was said to be a cylinder which is sufficiently resilient to provide resistance to deformation under a force of compression and substantially to return to its undeformed state when the force of compression is removed. The resistance should resemble the kind of resistance a human body would provide.
The present invention is a particular compression piston construction which has been developed specifically for use in a C.P.R. manikin to simulate the resistance of a chest cavity. The piston construction permits one to manufacture pistons to simulate the chest resistance and dimensions of an adult or a child. Moreover, the piston is simple, cost effective and durable.